A wide variety of CMP polishing liquids for use in CMP (Chemical Mechanical Polishing) are already known. If these CMP polishing liquids are classified on the basis of the abrasive grains (polishing particles) contained therein, then known CMP polishing liquids include cerium oxide CMP polishing liquids containing cerium oxide (ceria) particles as the abrasive grains, silicon oxide CMP polishing liquids containing silicon oxide (silica) particles as the abrasive grains, aluminum oxide CMP polishing liquids containing aluminum oxide (alumina) particles as the abrasive grains, and resin particle-based CMP polishing liquids containing organic resin particles as the abrasive grains.
Semiconductor element production processes require a plurality of planarization steps, and the polishing target (removal target) substance differs in each of these steps. Accordingly, a different CMP polishing liquid is used depending on the polishing target. One step for producing a semiconductor element is a step of polishing and planarizing an insulating material such as silicon oxide. Examples of this step include an STI (shallow trench isolation) formation step and an interlayer insulation film planarization step and the like. Silicon oxide CMP polishing liquids are known as examples of CMP polishing liquids for polishing insulating materials, but in recent years, cerium oxide CMP polishing liquids have been attracting considerable attention as they enable a faster polishing rate of inorganic insulating materials.
Patent Literature 1 discloses that when cerium oxide particles are used for polishing an insulating material, higher speed polishing is possible when the crystallite size (crystallite diameter) of the cerium oxide particles is large and crystal strain is minimal, namely when the crystallinity is favorable, but also discloses that the polishing target film tends to be more prone to scratching. Patent Literature 2 discloses that by using cerium oxide for which the cerium oxide crystallinity has been adjusted to satisfy a suitable range as the polishing material, polishing scratches can be reduced while maintaining a high polishing rate, and that by ensuring that the amount of cerium oxide particles having a particle size of 3 μm or more is restricted to not more than 500 ppm by mass of solids, polishing scratches can be reduced.